Atomistic Insight into the Growth of Chiral Gold Clusters: A Theoretical Study

Chiral inorganic nanoparticles (NPs) possess enantiospecific properties that have broad potential applications. However, the mechanisms underlying the formation of chiral NPs, especially in the initial stage, have remained elusive at the atomic level. Here, we investigate the nucleation and growth processes of 85 Au atoms (Au85) in the presence of chiral (l-/d-cysteine, Cys) and achiral (propyltrimethylammounium chloride, PTAC) surface ligands by using atomistic molecular dynamics simulations. Subsequent circular dichroism (CD) spectral calculations demonstrate that Au85-l-Cys and Au85-d-Cys clusters are chiral enantiomers. The finding highlights the role of chiral surface ligands in inducing the enantioselective growth of chiral clusters. Further simulation shows that the Au85-PTAC cluster, in which the capping ligands are achiral, also exhibits CD signals. The calculation results indicate that the chirality in Au clusters originates from the geometrical distortions, and chiral surface ligands are optional for the formation of chiral clusters. This work provides insight into the fundamental processes governing the formation of chiral NPs.